Optical reporters such as fluorescent dyes and upconverting phosphors have been used to detect the presence of biomolecules such as proteins and DNA molecules. Up-converting phosphor particles (UCP) have been encapsulated in transparent polyacrylate micro-carriers which can bond with protein sensors via functional groups as described in U.S. Pat. No. 5,132,242. Silylation techniques have also been utilized for binding antibodies to UCPs. Biotin/avidin binding has been utilized to detect biotinylated deoxyribonucleic acid (DNA) by UCP particles with avidin molecules on their surfaces. Hapten/digoxigenin sandwich technology has also been used to indirectly detect the presence of DNA with modified UCP particles.
Heretofore, the covalent binding of UCP particles to DNA molecules of detectable sequence has not been known. Such particles would be useful for labeling and authenticating articles and materials. Thus, there is accordingly a need for methods for authenticating articles, where the methods utilize compositions comprising a light emitting up-converting phosphor particle linked to a sequenceable DNA molecule. The present invention satisfies these needs as well as others.